Magnetic tracker system and method for use for surgical navigation

Abstract

A method and system for magnetically tracking a device of interest generating a plurality of pre-determined multi-frequency signals. The method and system transmits a plurality of magnetic fields from a transmitter circuit based on the corresponding pre-determined multi-frequency signals. The magnetic fields propagating through an area of examination encompassing the device of interest and a magnetic sensor coupled to the device of interest. The method and system generate a sensor signal at the magnetic sensor indicative of field strength of the magnetic fields transmitted by the transmitter circuit. Further, the method and system determine a position of the magnetic sensor relative to the transmitter circuit based on the multi-frequency signals and the sensor signal.

What is claimed is: 
     
       1. A method for magnetically tracking a device of interest, the method comprising:
 generating a plurality of pre-determined multi-frequency signals, wherein the pre-determined multi-frequency signals are phase shifted with respect to each other; 
 transmitting a plurality of magnetic fields from a transmitter circuit based on the corresponding pre-determined multi-frequency signals, the magnetic fields propagating through an area of examination encompassing the device of interest and a magnetic sensor coupled to the device of interest; 
 generating a sensor signal at the magnetic sensor indicative of a field strength of the magnetic fields transmitted by the transmitter circuit; 
 determining a direction of the magnetic fields with respect to the magnetic sensor based on the phase shift between the pre-determined multi-frequency signals; 
 determining a position of the magnetic sensor relative to the transmitter circuit based on the multi-frequency signals and the sensor signal; 
 determining at least one of: a position and an orientation of the device of interest in relation to the determined position of the magnetic sensor; and 
 manipulating the device of interest to at least one of: a desired position and a desired orientation. 
 
     
     
       2. The method of  claim 1 , further comprising identifying at least one of the magnetic fields from the transmitter circuit based on at least first and second frequencies of the multi-frequency signals; and
 wherein the position of the magnetic sensor is determined from the at least one of the magnetic fields that is identified. 
 
     
     
       3. The method of  claim 1 , wherein the multi-frequency signals are at least one from a group comprising a chirp signal, a frequency modulated signal, pseudo-random bit sequence, frequency shift keying, multiple frequency shift keying, multi-tone multi frequency signaling, or a Golay code. 
     
     
       4. The method of  claim 1 , wherein the sensor signal includes a secondary component induced by a secondary magnetic field created by passive sources within the area of examination, the method further comprising excluding the second component from calculations of the position based on the multi-frequency signals. 
     
     
       5. The method of  claim 4 , further comprising isolating at least one of the magnetic fields transmitted by the transmit circuit from the sensor signal based on at least first and second frequencies of the multi-frequency signal and electrical characteristics of the passive sources; and
 wherein the position of the magnetic sensor is determined from the at least one magnetic fields that is isolated. 
 
     
     
       6. The method of  claim 1 , wherein the magnetic sensor is a magneto-resistive sensor. 
     
     
       7. The method of  claim 1 , further comprising receiving a field strength measurement of the magnetic field from a second magnetic sensor. 
     
     
       8. The method of  claim 7 , wherein the position of the magnetic sensor is determined using known relative positions of the first and second magnetic sensors. 
     
     
       9. The method of  claim 1 , wherein the transmitter circuit is coupled to at least three electromagnetic coils. 
     
     
       10. The method of  claim 1 , further comprising registering the position of the magnetic sensor with at least one medical image to form a position registered medical image. 
     
     
       11. A magnetic tracking system for tracking a device of interest, the system comprising:
 a transmitter circuit configured to generate a plurality of magnetic fields based on corresponding pre-determined multi-frequency signals, wherein the pre-determined multi-frequency signals are phase shifted with respect to each other, the magnetic fields propagating through an area of examination; 
 a magnetic sensor coupled to the device of interest, the magnetic sensor configured to generate a sensor signal indicative of a field strength of the magnetic fields transmitted by the transmitter circuit when positioned within the area of examination; 
 a controller configured to determine a position of the magnetic sensor relative to the transmitter circuit based on the pre-determined multi-frequency signals and the sensor signal, wherein the controller is further configured to determine a direction of the magnetic fields with respect to the magnetic sensor based on the phase shift between the plurality of pre-determined multi-frequency signals; and further wherein the controller is configured to determine at least one of: a position and an orientation of the device of interest in relation to the determined position of the magnetic sensor and manipulate the device of interest to at least one of; a desired position and a desired orientation. 
 
     
     
       12. The magnetic tracking system of  claim 11 , wherein the controller is further configured to identify at least one of the magnetic fields from the transmitter circuit based on at least first and second frequencies of the multi-frequency signals. 
     
     
       13. The magnetic tracking system of  claim 11 , wherein the multi-frequency signals are at least one from a group comprising of a chirp signal, a frequency modulated signal, pseudo-random bit sequence, frequency shift keying, multiple frequency shift keying, multi-tone multi-frequency signaling, or a Golay code. 
     
     
       14. The magnetic tracking system, of  claim 11 , wherein the sensor signal includes a secondary component induced by a secondary magnetic field created by passive sources within the area of examination, the controller is further configured to exclude the second component from calculations of the position based on the multi-frequency signals. 
     
     
       15. The magnetic tracking system of  claim 14 , wherein the controller is further configured to isolate at least one of the magnetic fields transmitted by the transmit circuit from the sensor signal based on at least first and second frequencies of the multi-frequency signals and electrical characteristics of the passive sources. 
     
     
       16. The magnetic tracking system of  claim 11 , wherein the magnetic sensor is a magneto-resistive sensor. 
     
     
       17. The magnetic tracking system of  claim 11 , further comprising a second magnetic sensor, wherein the controller is further configured to determine the position of the magnetic sensor relative to the second magnetic sensor. 
     
     
       18. The magnetic tracking system of  claim 11 , wherein the transmitter circuit is coupled to at least three electromagnetic coils.